An apparatus for the continuous cracking of hydrocarbons in a thermal manner is disclosed in Schmalfeld et al, U.S. Pat. No. 3,215,505, wherein an upflow regenerator acts to recondition heat transfer particles, such as sand in an elongated pneumatic elevator for passage, after separation, with vapors into a thermal cracking reactor. The inlet channel for the heat carrier material discharges into the top of a pyrolytic reactor having an internal baffle structure to overcome problems of gas bubbles propelling the heat transfer material in an upward direction. In a preferred embodiment of the patentees applicable hydrocarbons, which are to be pyrolytically cracked, are passed into the sand bed from below same by a plurality of nozzles situated equi-distant across the cross section width of the reactor. These baffle structures, which are the essence of the patentees' invention, are existent to insure a pressure drop through the reactor chamber. This is antithetical to applicant's catalytic downflow reactor with an applicable pressure differential means situated at the top thereof so as to insure a near zero pressure drop throughout the downflow cracking reactor.
Another method and apparatus for the conversion of liquid hydrocarbons in the presence of a solid material, which may be a catalyst, is disclosed in U.S. Pat. No. 2,458,162, issued to Hagerbaumer. In FIG. 2, a downflow reactor is exemplified with solid particles derived from a dense phase surmounted bed in contact with a liquid charge entered approximately mid-way in the converter column after a control acts on the amount of catalytic material admitted to the converter unit. The amount of descending catalyst is controlled to provide an adequate level of a relatively dense phase of catalyst in the bottom of the reactor. The spent catalyst is reconverted to fresh catalyst in a catalyst reconditioner and then charged to the dense phase catalyst hopper surmounting the converter via a conveyor. Succinctly, this disclosure lacks appreciation of a downflow reactor as hereinafter described with a near zero pressure drop and a horizontal cyclone separator means used to convey regenerated catalyst to the top of the downflow reactor.
Two U.S. patents issued to Tyson U.S. Pat. Nos. 2,420,632 and 2,411,603 demonstrate the use of a reaction zone having a serpentine flow pattern defined by intermittent baffle sections. All of the above references are indicative of various antiquated reactors very distinct from the riser reactors used in contemporary refining practice. In fact, during the last 25 years the advent of the upflow riser reactor has attained near worldwide acceptance particularly in light of the very rapid deactivation rates of various very active zeolite catalysts. The prior art is replete with various techniques of using an upflow catalytic riser for the cracking of hydrocarbons. For example, see Owen, U.S. Pat. No. 3,849,291. The combination of this type of cracking, in addition to a downflow cracking unit, is exemplified by Payne et al U.S. Pat. No. 3,351,584 wherein cracking can take place in a lift pipe or in a downflow cracking reactor containing a dense bed of catalyst material. This prior art has failed to teach a catalytic cracking apparatus without baffles or stages, in a downflow reactor having a near zero pressure drop as a result of the conjunct interaction of an upflow riser regenerator and a downflow catalytic cracking unit interconnected by a horizontal cyclone separator.
A downflow catalytic cracking reactor in communication with an upflow regenerator is disclosed in Niccum et al U.S. Pat. No. 4,514,285 to reduce gas and coke yields from a hydrocarbonaceous feed material. The reactor will discharge the reactant products and catalysts from the reaction zone axially downward directly into the upper portion of an unobstructed ballistic separation zone having a cross sectional area within the range of 20 to 30 times the cross sectional area of the reaction zone. While there will be less coke formed during this type of downflow reaction wherein the catalyst moves with the aid of gravity, coke will still be formed in relatively large quantities. To permit this type of discharge into an unobstructed zone from the bottom of the downflow reactor invites serious "after cracking" pursuant to the extended contact time of the catalyst with the hydrocarbon material. The instant invention is an improvement over Niccum et al by providing specifically obstructed discharge of the downflow reactor comprising a horizontal cyclone separator to divide the catalyst from the hydrocarbon at a time selective for minimum contact of the two entities.
In Larson, U.S. Pat. No. 3,835,029, a downflow concurrent catalytic cracking operation is disclosed having increased yield by introducing vaporous hydrocarbon feed into downflow contact with a zeolite-type catalyst and steam for a period of time of 0.2 to 5 seconds. A conventional stripper and separator receive the catalyst and hydrocarbon products and require an additional vertical-situated cyclone separator to efficiently segregate the vapors from the solid particles.